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Dynamic Graphic Images, with Filled Regions
This code snippet shows the essential PG code to check student answers that are equations. Note that these are insertions, not a complete PG file. This code will have to be incorporated into the problem file on which you are working.
| PG problem file | Explanation |
|---|---|
DOCUMENT();
loadMacros("PGbasicmacros.pl",
"PGchoicemacros.pl",
"PGanswermacros.pl",
"PGgraphmacros.pl",
"PGnumericalmacros.pl",
"extraAnswerEvaluators.pl",
"weightedGrader.pl"
);
TEXT(beginproblem());
install_weighted_grader();
$showPartialCorrectAnswers = 1;
|
Initialization:
To do ..(what you are doing)........., we don't have to change the
tagging and documentation section of the problem file.
In the initialization section, we need to include the macros file |
# Construct a graph for the left endpoint Riemann sum,
# define the function to be graphed, and add it to the graph
$graphL = init_graph(-1,-1,9,9,ticks=>[10,10],axes=>[0,0],pixels=>[400,400]);
$c = random(8,12,1); # a constant for scaling the function
$f = FEQ("x**2/$c for x in <-1,9> using color:blue and weight:2");
$ftex = "\frac{x^2}{$c}";
# the parentheses around $fRefL are necessary
($fRefL) = plot_functions( $graphL, $f );
# Generate arrays of x and y values for the Riemann sum.
# There are n+1 entries in each array so that we can use
# only one pair of arrays for both the left and the right
# endpoint Riemann sums.
$a = random(2,4,1); # left endpoint of interval
$b = $a+4; # right endpoint of interval
$n = 8; # number of rectangles
$deltax = ($b - $a)/$n;
foreach $k (0..$n) { $x[$k] = $a + $k * $deltax; }
foreach $k (0..$n) { $y[$k] = &{$fRefL->rule}($x[$k]); }
# Graph the left endpoint Riemann sum
$lightblue = $graphL->im->colorAllocate(148,201,255);
$darkblue = $graphL->im->colorAllocate(100,100,255);
# Create arrays of pixel references for x and y values
foreach $k (0..8) {
$xpixL[$k] = $graphL->ii($x[$k]);
$ypixL[$k] = $graphL->jj($y[$k]);
}
$xaxisL = $graphL->jj(0);
# Plot the rectangles in the Riemann sum
foreach $k (0..$n-1) {
$graphL->im->filledRectangle($xpixL[$k],$ypixL[$k],$xpixL[$k+1],$xaxisL,$lightblue);
$graphL->im->rectangle($xpixL[$k],$ypixL[$k],$xpixL[$k+1],$xaxisL,$darkblue);
}
$graphL->lb(new Label ( 8.5,0,'x','black','right','top'));
$graphL->lb(new Label ( -0.25,8.5,'y','black','right','top'));
# Construct a graph for the right endpoint Riemann sum
$graphR = init_graph(-1,-1,9,9,ticks=>[10,10],axes=>[0,0],pixels=>[400,400]);
# the parentheses around $fRefR are necessary
($fRefR) = plot_functions( $graphR, $f );
# Graph the right endpoint Riemann sum
$lightblue = $graphR->im->colorAllocate(148,201,255);
$darkblue = $graphR->im->colorAllocate(100,100,255);
# Create arrays of pixel references for x and y values
foreach $k (0..8) {
$xpixR[$k] = $graphR->ii($x[$k]);
$ypixR[$k] = $graphR->jj($y[$k]);
}
$xaxisR = $graphR->jj(0);
# Plot the rectangles in the Riemann sum
foreach $k (1..$n) {
$graphR->im->filledRectangle($xpixR[$k-1],$ypixR[$k],$xpixR[$k],$xaxisR,$lightblue);
$graphR->im->rectangle($xpixR[$k-1],$ypixR[$k],$xpixR[$k],$xaxisR,$darkblue);
}
$graphR->lb(new Label ( 8.5,0,'x','black','right','top'));
$graphR->lb(new Label ( -0.25,8.5,'y','black','right','top'));
|
Setup:
We specify that the Context should be Notes: on using this and related Contexts. |
BEGIN_TEXT
The rectangles in the graph below illustrate a left endpoint Riemann sum for \( \displaystyle f(x) = $ftex \) on the interval \( \lbrack $a, $b \rbrack \).
$BR
The value of this left endpoint Riemann sum is \{NAMED_ANS_RULE('optional1',30)\},
and this Riemann sum is an \{ NAMED_POP_UP_LIST('optional2',['?','overestimate
of','equal to','underestimate of','there is ambiguity']) \} the area of the region enclosed by \(\displaystyle y = f(x) \), the x-axis, and the vertical lines x = $a and x = $b.
$BR
$BR
$BCENTER
\{ begintable(1) \}
\{ row( image( insertGraph($graphL), height=>400, width=>400, tex_size=>800 ) ) \}
\{ row("Left endpoint Riemann sum for \( y = $ftex \) on \( \lbrack $a, $b \rbrack \)") \}
\{ endtable() \}
$ECENTER
$BR
$HR
$BR
The rectangles in the graph below illustrate a right endpoint Riemann sum for \( \displaystyle f(x) = $ftex \) on the interval \( \lbrack $a, $b \rbrack \).
$BR
The value of this right endpoint Riemann sum is \{NAMED_ANS_RULE('optional3',30)\},
and this Riemann sum is an \{ NAMED_POP_UP_LIST('optional4',['?','overestimate of','equal to','underestimate of','there is ambiguity']) \} the area of the region enclosed by \(\displaystyle y = f(x) \), the x-axis, and the vertical lines x = $a and x = $b.
$BR
$BR
$BCENTER
\{ begintable(1) \}
\{ row( image( insertGraph($graphR), height=>400, width=>400, tex_size=>800 ) ) \}
\{ row("Right endpoint Riemann sum for \( y = $ftex \) on \( \lbrack $a, $b \rbrack \)") \}
\{ endtable() \}
$ECENTER
END_TEXT
|
Main Text: The problem text section of the file is as we'd expect. |
$LeftRiemannSum = 0;
foreach $k (0..$n-1) { $LeftRiemannSum = $LeftRiemannSum + $y[$k]; }
$LeftRiemannSum = $deltax * $LeftRiemannSum;
NAMED_WEIGHTED_ANS('optional1',num_cmp($LeftRiemannSum),45);
NAMED_WEIGHTED_ANS('optional2',str_cmp("underestimate of"),5);
$RightRiemannSum = 0;
foreach $k (1..$n) { $RightRiemannSum = $RightRiemannSum + $y[$k]; }
$RightRiemannSum = $deltax * $RightRiemannSum;
NAMED_WEIGHTED_ANS('optional3',num_cmp($RightRiemannSum),45);
NAMED_WEIGHTED_ANS('optional4',str_cmp("overestimate of"),5);
ENDDOCUMENT();
|
Answer Evaluation: As is the answer. |
